Process for purifying phenylenediamine derivatives



Patented Apr. 14, 1942 2.279.325 'PRocESsFoR-PURIFYING PHENYLENEDI- AMINE DERIVATIVES MarshalLIt-Brimer, Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of NewJersey NoDra'wing. Application December 23, 1940, Serial No. 571,397v

This invention relates to a process for purifying phenylenediamine derivatives.

It is known the N,N-dialkyl derivatives of pphenylene'diamine are formed, together with other products, when. hydroquinone is condensed, With-the elimination of Water, with primary alkyl or secondary alkyl primary amines, containing at least four carbon atoms, as shown in" United StatesPatent 2,163,639, dated June 2'7, 1939. It is fur'ther knownthat from such condensation products, N,N'-dialkyl-p-phenylenediamines can b'e'ob'ta'ined by aprocess comprising (1;) treating the condensation products with an alkali, such as an alkali metal hydroxide, (2) extracting the so treated condensation product with ahydrocarbon or ether solvent, and (3) removing the solvent-from the extract to obtain the phenylenediamine derivative, as shown in the copending-application of Von Bramer and A. 0. Buggles,-Serial No. 275,718, filed May 25, 1939.

It h'a-s been found that to increase the quantity of phenylenediamine derivatives 'in'the aforesaid condensation products tothe point where the condensation products provide an economical source of the phenylenediamine derivatives, severe conditions, such as increased temperatures, must be employed during the preparation of the condensation products. However, when such conditions are employed, the phenylenediamine derivatives obtained from the condensation products are usually contaminated with undesirable colored impurities which cannot be effectively removed by distillation. I have now found a method for removing these colored impurities from the phenylenediamine derivatives.

It is, accordingly, an object of my invention to provide a process for purifying phenylenediamine derivatives. Other objects will become apparent hereinafter.

In accordance with my invention, I remove colored impurities from a N,N-dialkyl-p-phenylenediamine obtained from a condensation product produced by condensing, with the elimination of water, hydroquinone with a primary amine selected from the group consisting of primary alkyl and secondary alkyl primary amines containing at least four carbon atoms, by treating a salt of the phenylenediamine derivative with an alcohol selected from the group consisting of methyl, ethyl and isopropyl alcohols. The colin the alcohol, and then, to treat the solution with an acid. The salt of the phenylenediamine derivative separates out, while the colored impurities remain'in solutioni It is also advantaored impurities pass into solution in the alcohol leaving the salt of the phenylenediamine derivative.

In practice, I have found it advantageous to dissolve the impure phenylenediamine derivative geous, in practice, to-a'dd the phenylenediamine derivatives to an alcoholic solution of an "acid; in which case the colored impurities pass'into'solution, while the salt of the phenylenediamine derivative separates out. However the treatment is carried out, the alcohol'containing the colored impurities can be readily removed from the salt of the phenylenediamine derivative, leaving the saltin a pure form.

The phenylenediamine derivative can thenbe freed from its salt by treating an aqueous solution of the salt with a bas'asuch as an alkali metal carbonate. The phenylenediamine'deriv'atives separate from the aqueous 'soluti'on'a's' oils which can the'nbe obtained as nearly'cdlorless, viscid liquids, by'distillation at pressures of from 0.1 to 0.2 mm.,0f mercury.

As acids for carrying out my process, hydrochloric, sulfuric, phosphoric and acetic are 'exemplary; I have found that hydrochloric acid is advantageously employed, and that an alcoholic solution of hydrogen chloride is especially suitable.

The following example will serve to illustrate the manner of practicing my invention.

Ewample 110 g. of N,N-di-(secondary butyD-p-phenylenediamine (obtained by condensing, with the elimination of water, hydroquinone with secondary butyl primary amine) were dissolved in one liter of isopropyl alcohol. To the resulting solution g. of 36% hydrochloric acid were added. The mixture was stirred and the salt of the phenylenediamine derivative was collected on a filter.

The salt of the phenylenediamine derivative was dissolved in one liter of water. The resulting solution was treated with solid sodium carbonate to free the phenylenediamine derivative from its salt. The phenylenediamine derivative separated out as an oil. The oil was separated from the aqueous liquors, and then subjected to distillation at a pressure of from 0.1 to 0.2 mm. of mercury, whereupon it was obtained as a nearly colorless viscid liquid.

In a manner similar to that illustrated in the foregoing example, phenylenediamine derivatives obtained from condensation products produced by condensing, with the elimination of water, hydroquinone with primary normal butyl priand secondary alkyl primary amines containing I at least four carbon atoms, comprising treating a salt of the phenylenediamine derivative with an alcohol selected from the group consisting of methyl, ethyl and isopropyl alcohols. I

2. A process for removing colored impurities from a N,N'-dialkyl-p-phenylenediamine -obtained from a condensation product produced by condensing, with the elimination of water, hydroquinonewith a primary amine selected from the group consisting of primary alkyl amines and secondary alkyl amines containing at least four "carbon atoms, comprising treating a'hydrochloride :of the phenylenediamine derivative with an alcohol selected from the group consisting of methyl, .ethyl and isopropyl alcohols.

'3..A process for removing colored impurities from a N,N'-di-(secondary aIkyD-p-phenylenediamine obtained from a condensation product produced by condensing, with the elimination of water, hydroquinone with a secondary alkyl primary amine containing at least four carbon *atoms, comprising treating a salt of the phenylenediamine derivative with an alcohol selected from the group consisting of methyl, ethyl and isopropyl alcohols.

4.. A process for removing colored impurities :from a N,N-di-(secondary alkyl)-p-phenylenediamine obtained from a condensation product produced by condensing, with the elimination of .water, hydroquinone with a secondary alkyl pri- ,mary amine containing at least four carbon ethyl and isopropyl alcohols.

atoms, comprising treating a hydrochloride of the phenylenediamine derivative with an' alcohol selected from the group consisting of methyl, ethyl and isopropyl alcohols.

5. A process for removing colored impurities from a N,N-di-(secondary butyD-p-phenylenediamine obtained from a condensation product produced by condensing, with the elimination of water, hydroquinone with secondary butyl primary amine, comprising treating a salt of the phenylenediamine derivative with an alcohol selected from the group consisting of methyl, ethyl and isopropyl alcohols.

6. A process for removing colored impurities from a N,N'-di-(secondary butyD-p-phenylenediamine obtained from a condensation product produced by condensing, with the elimination of water, hydroquinone with secondary butyl pri-' mary amine, comprising treating a hydrochloride of the phenylenediamine derivative with an alcohol selected from the group consisting of methyl,

'7. A process for removing colored impurities from a N,N'-di-(secondary butyl) -p-phenylenediamine obtained from a condensation product produced by condensing, with the elimination of water, hydroquinone with secondary butyl primary amine, comprising dissolving thephenyl- 'enediamine derivative in an alcohol selected from the group consisting of methyl, ethyl and isopropyl alcohols, and adding to the resulting solution an acid which forms a salt with the phenylenediamine derivative.

8. A process for removing colored impurities from a N,N'-di-(secondary butyD-p-phenylenediamine obtained from a condensation product produced by condensing, with the elimination of water, hydroquinone with secondary butyl primary amine, comprising dissolving the phenylenediamine derivative in an alcohol selected from the group consisting of methyl, ethyl and isopropyl alcohols, and adding to the resulting solution hydrochloric acid.

MARS HALL R. BRIMER. 

